This is the common willow of Waikato rivers. Only male crack willow occurs in the Waikato so no seed is set. The branches break off easily and readily establish roots. This is the only method of dispersal but it is effective enough to establish willow as the dominant tree on riverbanks and wet areas. Although willow competes with planted native plants, weeds like black nightshade (Solanum nigrum), inkweeed (phytolacca octandra), pampas (Cortaderia spp.) and Woolly nightshade (Solanum mauritianum) are more affected by their shade, so the willow confers a competitive advantage to the planted native plants, keeping the other weeds at bay.

Control: Initially the willow should have the lower branches removed to provide access to other weeds beneath. After a sub canopy is established in the planting, the options are to drill a series of ten mm holes in the trunk and fill with glyphosate herbicide, cut the bark and

paint herbicide on the cuts, cut down and remove the willow or allow

to remain and allow the taller native trees to grow taller and eventually

shade out the willow. It seems a good idea to try each of the options

to determine which works best on each site